Pierre Schaeffer was the first personal to identify that we listen to different sounds in different ways. Often when we hear we listen out for the source of the sound, the object or process that is causing the sound. Such listening would be described as contextual listening. Sometimes we listen to sounds and focus upon the sounds themselves independent from their source, this is heightened listening. Sometimes we listen to the sounds themselves and their inner musical (pitch and timbre) characteristics, free from contextual associations, this is Musical listening.